The present invention concerns a water-cooling system for direct chill semi-continuous casting equipment for casting metal.
Casting equipment of the above type for casting circular aluminium ingots comprises a large number of chills arranged in rows in a frame structure. Molten metal is supplied to the chills via a metal manifold through a hot-top from above and to the mould chamber in each chill. The metal is cooled and hardened in two stages. Stage 1 is called primary cooling in which the initial hardening of the metal is achieved by cooling through the wall of the mould chamber of the chill. Stage 2 is called secondary cooling in which water immediately below the primary cooling area is sprayed directly against the metal via a water gap or holes along the circumference of the chill. A movable support under each chill moves downwards as the metal hardens so that a long body, a circular ingot, is formed which may have different diameters depending on the purpose for which it is intended.
The cooling in the primary area in the chill is brought about by water, which, in accordance with a prior art technique, is also used for secondary cooling, first circulating through a chamber on the outside of the mould chamber. This chamber is formed by assembling chill elements with intermediate seals. Even if, when assembling the casting equipment, great efforts are made to ensure a good seal, leakages may still occur over time on account of material failure or incorrect assembly. If water comes into contact with molten metal, explosions may occur in the worst case scenario. This may result in serious damage or injury.
Another disadvantage of prior art equipment of this type is that, after each casting operation, the cooling water must be circulated through the secondary cooling circuit in the chills for a while in order to cool (recool) the chills and thus prevent thermal damage to the seals and other equipment components such as wall elements. During the time it takes to cool the casting equipment after casting, the cast rods cannot be removed from the equipment, which, in turn, results in an unnecessary delay before the next casting operation can begin and thus makes the casting equipment less efficient.
U.S. Pat. No. 4,597,432 shows and describes equipment of the above type in which any leaked water is drained upwards towards the top of the frame structure of the chills and out over the side of it. Although there is a certain distance from the top of the frame structure up to the melt in the metal distribution channel, this solution represents a not inconsiderable risk of accidents in connection with water splashes near the melt.
Moreover, the solution does not have a warning system for leaks or a solution for the elimination of the delay between casting operations.
The present invention represents casting equipment which is considerably improved in terms of safety, which is more efficient and which is easy and inexpensive to produce.
The present invention is characterised by the features defined in the characterising parts of the attached independent claims 1 and 3.
The dependent claims 2, 4 and 5 indicate the advantageous features of the present invention.